This invention relates generally to a gas nozzle for a heat treating furnace, and more particularly, for a heat treating furnace of the type in which a cooling gas flows from a gas directing construction or plenum into the work chamber through a large number of nozzles after the workpieces have been heated. One example of this general type of heat treating furnaces can be found in Jones, et al., U.S. Pat. No. 4,395,832.
In the above mentioned U.S. Pat. No. 4,395,832, each nozzle is externally threaded inserted through the wall of the gas directing device or plenum, and held in place by a lock nut on each side of that wall. This limits the materials used to those suitable for threading and limits the furnace design to those which provide easy access to both sides of the nozzle attachment point on the plenum.
In Moller and Wolter U.S. Pat. No. 4,560,348, the resilience of the nozzle material is relied upon for insertion or removal, a special tool is used to compress it for insertion or removal, and a flare at one end or another provides retention. The fact that it must be compressed for insertion or removal limits the materials suitable for its construction to those which are resilient, such as molybdenum. However, because molybdenum becomes extremely brittle and non-resilient once heated to normal working temperatures for this type of furnace, the very act of attempting to compress a molybdenum or similar nozzle after initial use could shatter it, making it totally unfit for re-use. This is especially true with the flared nozzle design of U.S. Pat. No. 4,560,348, which would require the nozzle to be compressed to about one-half its expanded diameter for removal. Also, it is very difficult to draw molybdenum to form a flare.